Coolant Temperature Sensor (CTS)

Most engine functions are effected by the coolant temperature. Determining whether the engine is hot or cold is largely dependent on the temperature of the coolant. An accurate temperature signal to the ECM is supplied by the coolant temperature sensor. The coolant temperature sensor is a thermistor mounted in the engine coolant stream. A thermistor is an electrical device that varies its resistance in relation to changes in temperature. Low coolant temperature produces a high resistance (100,000 ohms at -40°F/-40°C) and high coolant temperature produces low resistance (70 ohms at 266°F/130°C). The ECM supplies a signal of 5 volts to the coolant temperature sensor through a resistor in the ECM and measures the voltage. The voltage will be high when the engine is cold and low when the engine is hot.

TESTING

Disconnect the negative battery cable.

Disconnect the coolant temperature sensor wire connector.

Connect a volt/ohmmeter to the terminals of the coolant temperature sensor and verify the reading is within range on the appropriate diagnostic CODE chart.

REMOVAL & INSTALLATION

Disconnect the negative battery cable.

Drain the cooling system into a clean container for reuse.

Disconnect the electrical connector from the coolant temperature sensor.